Estimation of Deepwater Horizon Oil Spill Effects on Population Dynamics of the Loggerhead Sea Turtle (Caretta caretta)

Abstract

Deepwater Horizon (DWH) was the largest offshore oil spill in US history. The result was approximately 3.19 million barrels of oil being released into the ocean. Deepwater Horizon significantly affected the Gulf of Mexico and surrounding beaches, including threatened and endangered marine life such as the loggerhead sea turtle. Hence, we conducted a thorough literature review to obtain the demographic data and developed a stage-structured stochastic population dynamics model using STELLA® 7.0.1 for loggerhead sea turtles. We modeled three conservation scenarios along with a baseline scenario. Then we subjected the conservation scenarios to added oil mortality. We then used the model to quantify the potential effects of oil spills on the population of loggerhead sea turtles for the next decade. The results of the baseline model without oil effects show a decrease in the adult population from 119 in 1987 to 13 in 2026, implying the possibility of the population’s extinction without any conservation efforts. All three conservation scenarios without oil effects show an increase over 40 years. Conservation scenarios after added linearly decreasing oil mortality from 2010 to 2019 all decreased about 79% in 2026 at the end of our 40-year simulation. Continued conservation efforts and assessments of loggerheads will ensure population numbers continue to recover following DWH.